Shrinking device

ABSTRACT

The invention relates to a shrinking device ( 2, 70 ) for shrinking a tool ( 12 ) into a tool holder ( 11, 68 ) of a tool chuck ( 10 ), said device comprising a heating device ( 14, 52, 72 ) for heating the tool holder ( 11, 68 ). The invention is characterised in that the shrinking device ( 2, 70 ) comprises a gas suction unit ( 16 ) for evacuating the gases ( 32, 84 ) that escape from the tool holder ( 11, 68 ).

PRIOR ART

The invention relates to a shrinking device and to a method forshrinking a tool into a tool holder of a tool chuck.

When a tool is shrunk, the tool is thermally clamped into a tool holderof a tool chuck, as a result of which a very firm and highly precisefixing of the tool, for example a drill, milling cutter or the like, inthe tool holder can be achieved. In this case, the tool holder, whichhas, for example, a hole for receiving a tool shank, is heated, so thatthe tool holder expands. The tool is inserted by its shank into the holeenlarged by this means. During subsequent cooling, the tool shank isheld frictionally in the tool holder, which is shrunk on account of thecooling. The diameters of the hole of the tool holder and of the shankof the tool are selected here in such a manner that a frictional androtationally fixed connection is produced during cooling. Tools shrunkin such a manner are used in metal machining and at speeds of rotationof over 10 000 revolutions per minute.

DE 100 24 423 A1 discloses a shrinking device for shrinking a tool intoa tool holder, which device has an induction coil as the heating devicefor heating the tool holder.

The invention is based, in particular, on the object of specifying animproved shrinking device in comparison to known shrinking devices. Thisobject is achieved by the features of patent claim 1. Furtherrefinements emerge from the subclaims.

ADVANTAGES OF THE INVENTION

The invention is based on a shrinking device for shrinking a tool into atool holder of a tool chuck, having a heating device for heating thetool holder. It is proposed that the shrinking device comprises a gassuction device for evacuating gases escaping from the tool holder.

Over the course of time, a multiplicity of tools are shrunk into a toolchuck. These tools are used together with the tool chuck during amachining operation on a workpiece. In this connection, the tools aregenerally wetted with a cooling or cutting liquid, usually with aspecial oil or with an emulsion. The liquid flows along the outside ofthe tool or through cooling ducts in the interior of the tool. As arule, this liquid also comes into contact with the tool chuck which alsocan likewise be provided with cooling ducts. After use, the tool isunshrunk from the tool holder by the tool holder being heated again, inwhich case the hole of the tool holder is enlarged and the tool with itsshank can be pulled out of the tool holder. Residues of a liquid in oron the tool or in or on the tool holder are heated at the same time inthis case. The shrinking or unshrinking temperature is usually aroundapprox. 250° C. and therefore above the boiling temperature of thenormally used cooling or cutting liquids. The liquid residues at leastpartially evaporate and propagate in the surroundings of the shrinkingdevice. The evaporating gases rising out of the tool holder or from thesurface of the tool do not always smell pleasant and may even constitutea health risk.

With a gas suction device, which is arranged on the tool holder and isintended for evacuating gases escaping from the tool holder, these gasescan be guided away from the tool holder and supplied to a filter. Thegases are at least predominantly removed from the ambient air and can besupplied to a cleaning process. The gas suction device is expedientlyarranged on the heating device or the tool chuck and/or can be connectedto them. It suffices here if part of the gas suction device is arrangedon the tool chuck or on the heating device and/or can be connected tothem.

The gas suction device has a fan for generating a pressure or a negativepressure and expediently it has a gas-cleaning device or filter device.It is also possible to supply the evaporating gases in uncleaned form toa container or to a surrounding region situated at a distance. The gassuction device can be considered as belonging to the shrinking device atleast insofar as a gas inlet opening of the gas suction device can beassigned directly to the shrinking device. This gas inlet opening can bepositioned in the direct vicinity of a holder opening of the toolholder, so that the gases which rise from the tool or out of the toolholder and are charged with liquid vapor are at least predominantlysucked into the gas inlet opening. An escape of the gases into thesurroundings is effectively counteracted.

The shrinking device expediently comprises a gas-conducting unit forconducting gas from the holder opening of the tool holder to a gas inletopening of the gas suction device. With a gas-conducting unit, vaporsarising at various locations can be conducted to the gas inlet opening,so that, for example, just one gas inlet opening can be used to evacuatevapors rising from surfaces at different orientations from one anotheror from relatively large surfaces. The gas-conducting unit may be afunnel which opens into the gas inlet opening, or it may be a structurewhich is designed in a different manner, at least partially encompassesa gas volume and through which the encompassed gas volume is directed tothe gas inlet opening during the operation of the gas suction device. Inthis case, the gas-conducting unit can at least partially encompass thetool and/or the tool holder. It is also possible for the gas-conductingunit to essentially completely surround the tool and to at leastpartially surround the tool holder.

The shrinking device advantageously comprises a gas-conducting unitwhich encompasses a negative pressure region, the gas-conducting unitbeing provided for maintaining a negative pressure in the negativepressure region relative to an external region of the gas-conductingunit and a pressure drop from a receiving opening of the tool holder tothe negative pressure region. The gas-conducting unit is designed insuch a manner that, by means of the evacuation of gas from thegas-conducting unit, a negative pressure is produced within thegas-conducting unit and is maintained in the entire region by the shapeof the gas-conducting unit during continuous evacuation of gas. By meansof the, if appropriate, only slight negative pressure in the interior ofthe gas-conducting unit, the gas, which is mixed with residue vapors, inthe interior of the gas-conducting unit is obstructed from emerging insignificant quantities out of the gas-conducting unit into thesurroundings, which are characterized by higher pressure. Reliableprotection against emerging gases can be achieved. The gas-conductingunit encompasses the negative pressure region in such a manner that thenegative pressure is retained. In this case, it can completely or onlypartially close off the negative pressure from the surroundings. Itadvantageously shields to the outside a region around the opening of thetool holder in order to maintain a negative pressure. The gas-conductingunit in each case at least partially surrounds, for example, only thetool and/or the tool holder. It is also possible for the gas-conductingunit to enclose the entire shrinking device or, if the shrinking deviceshould be part of an apparatus, the entire apparatus.

The gas-conducting unit may have one or more openings through which thetool and, if appropriate, the tool holder or other parts of theshrinking device can protrude out of the gas-conducting unit or canprotrude into the latter.

The gas suction device, if appropriate with a gas-conducting unit, maybe arranged separately from the heating device and designed in a mannersuch that it can move independently of the heating arrangement. However,in one advantageous refinement, the heating device annularly encompassesthe tool holder, and the gas-conducting unit is designed as a hood onthe heating device. The heating device can therefore serve as a supportfor the gas-conducting unit which, as a result, does not have to beequipped with a dedicated suspension means or moveable fastening. Thegas-conducting unit may be connected loosely or fixedly to the heatingdevice. A loose gas-conducting unit may be taken away and returnedseparately from the tool holder. A gas-conducting unit connected fixedlyto the heating device may be used as the suspension means and, ifappropriate, the movement device of the heating device. A stablearrangement of the gas-conducting unit can be achieved without a furtherand separate suspension means.

A saving on components can also be achieved by the heating deviceforming part of the gas-conducting unit. In this case, thegas-conducting unit is arranged on the heating device during theevacuation operation, in which case a surface of the heating device,which surface faces the gas-conducting unit, serves to conduct the gaswhich is to be evacuated to a gas inlet opening.

In a further variant embodiment of the invention, the gas suction devicehas a gas inlet opening which is arranged in the interior of the toolholder. The vapors produced in the tool holder are thereby sucked oninto the interior of the tool holder and to the gas inlet opening andare obstructed from emerging out of the opening of the tool holder intothe surroundings. In the case of such a refinement of the shrinkingdevice, a gas-conducting unit may be omitted, as a result of which freermobility of the heating device can be achieved. In addition, the tooltogether with the tool holder can be set down at a location provided forthe evacuation of gas, at which the tool is mounted or cooledtransiently, for example, with it furthermore being possible for vaporsescaping from the shank of the heated tool to be evacuated.

In order, with the tool situated in the tool holder, to ensure a flow ofgas into the tool holder and to the gas inlet opening, it is expedientto design ducts for the supply of air in the tool holder. Ducts of thistype may be incorporated, for example, in the inner surface of the toolholder, which surface faces the tool. It is also possible to provideducts at another location in the tool holder, through which gas can besucked from an external region of the tool holder, which region issituated at the tool shank, to the gas inlet opening. In the case of ashrinking device, in which the tool is first of all shrunk into ashrinking sleeve and the shrinking sleeve is shrunk into a shrinkingchuck, the ducts may be arranged on the inside, outside or in theshrinking sleeve.

In one particularly advantageous refinement of the invention, theheating device has gas ducts which are provided for gas to flow throughduring the operation of the gas suction device. The heating device canbe cooled by the gas, as a result of which the service life of theheating device is prolonged. The heating device is expediently cooledwith air. During the heating of the tool holder by the heating device,the heating device is heated at the same time by the heat radiated bythe tool holder. This results in an increased stress on the heatingdevice. In order to remove the gas, which is mixed with liquid vapors,from the closer surroundings of the tool holder, it is necessary tobring air or gas from the more distant surroundings of the tool holderin order to use the air flow caused in this manner to transport away thegas which is to be removed. The air flow from the more distantsurroundings of the tool chuck can be used for cooling the heatingdevice. By guiding the cool air through gas ducts of the heating device,cooling of this type can be achieved in an effective manner. The coolair flow is guided first of all through the heating device and then tothe gases which have escaped and are designated for transporting away.

The gas ducts are expediently connected to the negative pressure regionby a gas line. The air to be conducted through the heating device canthereby be guided in as effective a manner as possible through theheating device and is guided through the gas line into the region inwhich it transports the liquid vapors to a gas inlet opening. The designof the gas channels is therefore independent of the location at whichthe liquid vapors arise.

In an alternative refinement of the invention, the gas ducts open intothe negative pressure region. The air is therefore guided through thegas ducts into the immediate vicinity of the location at which thevapors arise and can then transport them away.

A further advantage is achieved if the tool chuck has an upper endsurface at one end of the tool holder and the gas-conducting unitcompletely surrounds the tool holder above the end surface. Vapors whichare heated and rise upward cannot escape out of the gas-conducting unitupward and can essentially be completely removed, for example throughthe gas inlet opening. For this purpose, the gas inlet opening can bearranged above the end surface, in which case the complete surroundingis also regarded as being satisfied in this case.

During heating of the tool holder, the majority of the gases willusually rise out of the holder opening. By means of a shielding elementfor resting on an upper end surface arranged at one end of the toolholder, the shielding element having a gas-conducting duct forconducting gas out of the tool holder opening, these gases can bedirected in a specific manner, for example to a negative pressure regionand/or to a gas inlet opening.

Multiple use of the shielding element can be achieved if the shieldingelement is provided for shielding a tool, which is inserted into thetool holder, from a magnetic field generated by the heating device. Anadditional magnetic-field-shielding element, which opposes a heating ofthe tool arranged in the holder opening, can be omitted.

A secure positioning of the heating device around the tool holder can beachieved if the shielding element is provided as a stop element forpositioning the heating device. The shielding element is expedientlyconnected fixedly to the heating device.

The shielding element can be provided for encompassing a tool arrangedin the holder opening. If, however, as in the case of a shrinkingprocess, no tool is arranged in the holder opening, a closing-offshielding element can be used. In this case, the shielding elementupwardly closes off the holder opening in such a manner that gasesrising out of the tool holder can only leave the holder opening upwardthrough at least one gas-conducting duct in the shielding element. Anundesirable outflow of vapors can be effectively opposed.

The invention is also based on a method for shrinking a tool into a toolholder, in which the tool holder is heated by a heating device. It isproposed that gases are evacuated from the tool holder with the aid of agas suction device. An undesirable propagation of gases rising out of orat the tool holder can be effectively opposed.

DRAWING

Further advantages emerge from the drawing description below. Thedrawing illustrates exemplary embodiments of the invention. The drawing,the description and the claims contain numerous features in combination.The expert will expediently also consider the features individually andput them together to form meaningful further combinations.

In the drawing:

FIG. 1 shows a schematic illustration of a tool setting and measuringapparatus with a shrinking device,

FIG. 2 shows a section through a shrinking device with a gas suctiondevice in a schematic illustration,

FIG. 3 shows an alternative embodiment to FIG. 2 of a heating device andgas-conducting device,

FIG. 4 shows a further embodiment of a gas suction device with ashielding element,

FIG. 5 shows a further sectional illustration of the gas suction devicefrom FIG. 4,

FIG. 6 shows a plan view of the shielding element from FIG. 5, and

FIG. 7 shows a sectional illustration of a further shielding element onthe tool holder.

DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

FIG. 1 shows a device which is designed as a tool setting and measuringapparatus and has a shrinking device 2. The device has a measuringdevice 4 for optically measuring tool parameters. The measuring device 4can be moved in the directions shown by the arrows 6. The device alsocomprises a rotatable tool chuck holder 8 for holding a tool chuck 10,which is designed as a shrinking chuck and has a tool holder 11 (FIG.2). A tool 12 is shrunk into the tool holder 11 by the shrinking device2 by a heating device 14 being arranged around the tool holder 11 andheating the tool holder 11. For this purpose, the heating device 14 canbe moved in accordance with the directions illustrated by the arrows 26.The heating device 14 operates on the eddy current principle andcomprises an induction coil for this. A gas suction device 16 whichcomprises a gas-conducting unit 18 and a gas line 20 connected theretois connected to the heating device 14. The gas line 20 opens into a fanunit 22 of the gas suction device 16, in which a cleaning device 24 forcleaning the gases flowing through it is integrated.

FIG. 2 schematically illustrates parts of the shrinking device 2 inenlarged form. A hole 30 is made in the tool holder 11 and is providedfor holding the tool 12. In order to shrink the tool 12 into the toolholder 11, the heating device 14, which is of annular design, isarranged around the tool holder 11. By means of an induction current,the metallic material of the tool holder 11 around the hole 30 isheated. The tool 12 is positioned above the hole 30 in a waitingposition. As the temperature of the metallic material rises, more andmore oil residues evaporate as gases 32 which are are retained in thehole 30 or on the tool holder 11 by a tool which has previously beenshrunk in the shrinking chuck. In particular when unshrinking the tool12, any residues from a machining process just ended that are stillmoist and adhere to the or in the tool 12 or tool holder 11 are heated.They evaporate and escape from the tool 12, from the tool holder 11 or,in the case of the tool 12 (as shown in FIG. 2) which has already beenlifted out of the hole 30, from the hole 30.

The gases 32 pass into a negative pressure region 36 around the opening34 of the tool holder 11 and, without the gas suction device 16, wouldbe distributed into the more distant surroundings. This furtherdistribution is prevented by the gas-conducting unit 18 which shieldsoff the negative pressure region 36 to the outside in order to maintaina negative pressure. By means of the fan unit 22, the gas line 20 and agas inlet opening 38, gas is evacuated from the negative pressure region36 shielded by the gas-conducting unit 18, so that a negative pressurein comparison to the external region of the gas-conducting unit 18 isproduced in this region. This negative pressure is maintained by thegas-conducting unit 18.

The gas evacuated through the gas inlet opening 38 is sucked up fromvarious openings of the gas-conducting unit 18. A first opening 40 inthe gas-conducting unit 18 serves to let through the tool 12 from aboveinto the hole 30 of the tool holder 11. The first opening 40 is designedin such a manner that, even with the tool 12 inserted, gas—usuallyambient air—can flow through the opening 40 into the negative pressureregion 36. A second opening 42 which is larger than the first opening 40is made on the underside of the gas-conducting unit 18. Like the firstopening 40, the second opening 42 also serves to let through the tool 12into the hole 30 and to supply air into the negative pressure region 36.

The air flowing in through the second opening 42 can flow from theoutside into the negative pressure region 36 through one or more slots44 between the tool holder 11 and the heating device 14. It is alsopossible for the tool holder 11 to have an inner hole 46 in which apositioning device (not shown specifically in the figures) can bearranged. Air sucked in can pass from the hole 46 into the hole 30 inorder to flow on from there through the opening 34 and the secondopening 42 into the negative pressure region 36. By means of the gas andair flows described, the liquid vapor arising at the tool 12 or the toolholder 11 is guided, directed by the gas-conducting unit 18, to the gasinlet opening 38 of the gas suction device 16. The vapors do not emergeinto the surroundings of the gas suction device 16.

A further air flow is guided directly through the heating device 14. Forthis purpose, the heating device 14 has gas ducts 48 through which aircan flow from one of the slots 44 through the heating device 14 and onto a gas line 50. The gas line 50 opens into the negative pressureregion 36 from where the air flow, carrying along the residue vapors, issucked to the gas inlet opening 38. The air flow directed through theheating device 14 causes a cooling of the heating device, which isheated by the radiation of heat from the tool holder 11. This coolingenables the service life of the heating device 14 to be prolonged. Thegas ducts 48, which are shown in sectional form in FIG. 2 and aredesigned as holes, run within the heating device in such a manner that,at the point which faces the tool holder 11 and is heated the most bythe latter, the cool air flows into the heating device 14. By thismeans, this point which is heated the most is cooled the most.

An alternative refinement of a heating device 52 and of a gas-conductingunit 62 is shown in FIG. 3. Gas ducts 54, 56, 58, of which three areshown in FIG. 3, are made in the heating device 52, which essentiallycomprises an induction coil. Air can flow from below the heating device52 through the heating device 52 directly into the negative pressureregion 60 of the gas-conducting unit 62 through the gas ducts 54, 56,58. The gas ducts 54, 56, 58 open directly into the negative pressureregion 60. In contrast to the gas-conducting unit 18 from FIG. 2, thegas-conducting unit 62 from FIG. 3 is essentially open downward towardthe heating device 52, so that air can flow out of the gas ducts 54, 56,58 without interference into the negative pressure region 60. The gasducts 54, 56, 58 are designed in such a manner that the widest gas duct58 is placed in the region in which there is the greatest formation ofheat. A second gas duct 56, which is of somewhat smaller design in senseof its cross section than the gas duct 58, is placed somewhat furtheraway from the heat-radiating tool holder (not shown). The gas duct 54having the smallest flow cross section is placed even further away. Theshape and routing away of the gas ducts 54, 56, 58 and 48 can bedesigned in a manner regarded as suitable by an expert. Thegas-conducting units 18 and 62 shown in FIGS. 2 and 3 are designed ineach case as a hood on the heating devices 14 and 52, respectively. Thegas-conducting unit 18 is fastened to the heating device 14 by means ofsmall stands 64. The gas-conducting unit 18 is therefore supported bythe heating device 14, with the result that it does not require aseparate suspension means. The gas-conducting unit 62 is designed suchthat it rests on the heating device 52, with it also being possible tofasten the gas-conducting unit 62 directly on the heating device 52. Thegas-conducting unit 62 is open downward, a surface of the heating device52 forming part of the gas-conducting unit 62. The gas-conducting unit62 has a suspension means (not shown in FIG. 3) by means of which thegas-conducting unit 62 can be moved separately from the heating device52 to a tool holder or a tool or away from the latter.

In an alternative refinement of the invention, it is also possible toconnect the fan unit 22 to the hole 46 in the tool holder 11 and toevacuate gases directly downward out of the hole 30 of the tool holder11. Residue vapors arising in the hole 30 are thus not able to emergefrom the hole 30 at all. In addition, an evacuation of gas can also becontinued if the heating device 14 is moved away from the tool holder11. In order to enable an evacuation of gas even when the tool 12 isshrunk in, ducts which are incorporated in the surface 66 of the hole 30can be provided, in which gas or air can flow in to the hole 46 fromabove the tool holder 11. By this means, an effective evacuation of gascan be achieved even when the tool is shrunk in.

FIG. 4 shows a further shrinking device 70, which is arranged around atool holder 68, with a heating device 72 designed as an inductor. Theheating device 72 is held by a housing 74 of the shrinking device 70which, in turn, has a hinged cover 76. In the locked state, the cover 76is supported on a shielding element 78, which is arranged in an openingof the cover 76 and rests on an upper end surface 80 of the tool holder68, which end surface is arranged at one end of the tool holder 68. Whenthe shrinking device 70 is lowered around the tool holder 68, theshielding element 78 serves as a stop for positioning the heating device72 in a position suitable for heating the tool holder 68.

In order to evacuate gases 84 rising in the holder opening 82 of thetool holder 68, two gas-conducting ducts 86 are placed in a cross-shapedmanner into the underside of the shielding element 78. FIG. 6 showsthese gas-conducting ducts 86 in a view from below of the shieldingelement 78. The gases 84 are directed through the gas-conducting ducts86 into a negative pressure region 88 which is connected by a gas inletopening 90 to a gas line 92 (FIG. 5). Gases 84 are evacuated from thenegative pressure region 88 through the gas line 92 and are supplied toa fan unit 22, for example as illustrated in FIG. 1. The gases 84flowing through the gas-conducting ducts 86 are sucked below asupporting element 94 and between webs 96 into the negative pressureregion 88. The webs 96 are connected integrally to the supportingelement 94 which, in turn, is connected fixedly to the shielding element78.

By means of the gas-conducting unit 98, which comprises the housing 74,the cover 76 and the shielding element 78 and completely surrounds thetool holder 68 above the end surface 80 up to the gas inlet opening 90,gases 84 rising upward out of the holder opening 82 cannot penetrate outof the gas-conducting unit 98 and into the surroundings. Evaporatinggases rising on the outside of the tool holder 68 are likewise suckedinto the negative pressure region 88 below the supporting element 94 orbetween the webs 96. The closed shielding element 78, which closes theholder opening 82 upward—up to the gas-conducting ducts 86—is suitablein particular for a shrinking operation, in which no tool 12 is arrangedin the holder opening 82 during the heating of the tool holder 68.

A shielding element 102 provided with a passage opening 100 is shown ina sectional illustration in FIG. 7. It likewise rests on the end surface80 of the tool holder 68 and comprises gas-conducting ducts 104, whichare arranged in a crosswise manner on its underside, for guiding gases84 rising out of the holder opening 82 to a negative pressure region 88(as illustrated in FIG. 4) encompassed by a gas-conducting unit 98. Theshielding element 102 is used in particular for unshrinking a tool 12out of the tool holder 68 and serves for shielding a tool 12, which isinserted in the holder opening 82, from a magnetic field generated bythe heating device 72, so that the tool 12 does not heat and expand toorapidly. By means of the suction drawing toward the negative pressureregion 88, gases 84 are prevented from passing through upward from theholder opening 82 through the passage opening 100, so that thesurroundings are also shielded from the gases 84 by the shieldingelement 102.

Reference Numbers

-   2 Shrinking device-   4 Measuring device-   6 Arrow-   8 Tool chuck holder-   10 Tool chuck-   11 Tool holder-   12 Tool-   14 Heating device-   16 Gas suction device-   18 Gas-conducting unit-   20 Gas line-   22 Fan unit-   24 Cleaning device-   26 Arrow-   30 Hole-   32 Gas-   34 Opening-   36 Negative pressure region-   38 Gas inlet opening-   40 First opening-   42 Second opening-   44 Slot-   46 Hole-   48 Gas duct-   50 Gas line-   52 Heating device-   54 Gas duct-   56 Gas duct-   58 Gas duct-   60 Negative pressure region-   62 Gas-conducting unit-   64 Stand-   66 Surface-   68 Tool holder-   70 Shrinking device-   72 Heating device-   74 Housing-   76 Cover-   78 Shielding element-   80 End surface-   82 Holder opening-   84 Gas-   86 Gas-conducting duct-   88 Negative pressure region-   90 Gas inlet opening-   92 Gas line-   94 Supporting element-   96 Web-   98 Gas-conducting unit-   100 Passage opening-   102 Shielding element-   104 Gas-conducting duct

1. A shrinking device for shrinking a tool into a tool holder of a toolchuck, the shrinking device comprising: a heating device for heating thetool holder; and a gas suction device for evacuating gases escaping fromthe tool holder.
 2. The shrinking device as claimed in claim 1, furthercomprising a gas-conducting unit for conducting gas from a holderopening of the tool holder to a gas inlet opening of the gas suctiondevice.
 3. The shrinking device as claimed in claim 1, furthercomprising a gas-conducting unit which encompasses a negative pressureregion, the gas-conducting unit being provided for maintaining anegative pressure in the negative pressure region relative to anexternal region of the gas-conducting unit and a pressure drop from aholder opening of the tool holder to the negative pressure region. 4.The shrinking device as claimed in claim 2, wherein the heating deviceannularly encompasses the tool holder and the gas-conducting unit isdesigned as a hood on the heating device.
 5. The shrinking device asclaimed in claim 2, wherein the heating device forms part of thegas-conducting unit.
 6. The shrinking device as claimed in claim 2,wherein the heating device has gas ducts which are provided for gas toflow through during the operation of the gas suction device.
 7. Theshrinking device as claimed in claim 3, wherein the gas ducts areconnected to the negative pressure region by a gas line.
 8. Theshrinking device as claimed in claim 3, wherein the gas ducts open intothe negative pressure region.
 9. The shrinking device shrinking deviceas claimed in claim 2, wherein the tool chuck has an upper end surfacearranged at one end of the tool holder and the gas-conducting unitcompletely surrounds the tool holder above the end surface.
 10. Theshrinking device as claimed in claim 1, further comprising a shieldingelement for resting on an upper end surface arranged at one end of thetool holder, the shielding element having a gas-conducting duct forconducting gas out of the holder opening.
 11. The shrinking device asclaimed in claim 10, wherein the shielding element is provided forshielding a tool, which is inserted into the tool holder, from amagnetic field generated by the heating device.
 12. The shrinking deviceas claimed in claim 10, wherein the shielding element is provided as astop element for positioning the heating device.
 13. The shrinkingdevice as claimed in claim 10, wherein the shielding element upwardlycloses off the holder opening in such a manner that gases rising out ofthe holder opening can only leave the holder opening upward through atleast one gas-conducting duct in the shielding element.
 14. A method forshrinking a tool into a tool holder of a tool chuck, the methodcomprising: heating the tool holder by a heating device; and evacuatinggases from the tool holder with the aid of a gas suction device.